1994 Supra Sunsport 5.8 Pro Boss Starting Problems

I have a 1994 Supra Sunsport with a 5.8 Pro Boss. I am having terrible starting issues. Upon launch, boat starts but is very hard to start. After it starts it will run fine. After it shuts down and upon attempting to start, it fires quickly then dies. It takes up to 5 minutes to get it restarted. Pulling off the flame arrestor, you can't see any gas coming out of the throttle body injectors. After a while, sometimes having to tap around the high pressure pump, fuel starts to squirt out of the injector and the boat will start.

We have replaced both fuel pumps and the fuel filter along with the fuel pump relay. Mechanics are perplexed. any help will be greatly appreciated.

Have you changed the canister filter.

yes. new filter when we got the two new fuel pumps. filter is low on the port side of the engine. had dealer do it.

Ok then find the fuel return line. Pinch it closed and see if it runs better. If it does one of your pumps was defective.

thanks! Will check out next time down at lake......

Let me know. My high pressure pump went bad last year and found the part was updated and the new pump wasn't right. Had to track down another manufacturer that made the same pump

I think we have a solution. There is an oil pressure sensor that allows the pumps to run for 15 seconds during starting. If it doesn't sense pressure indicating no start, it shuts down the fuel pumps, preventing burnout of the pumps. My sensor was intermittently shutting down during the starting process. Bypassing the switch seems to have fixed the issue. I am going down to the lake this weekend to see if the fix is actually going to work. I'm hopeful.

So the problems keep getting worse. Bypassing the oil pressure switch did allow starting but now the engine coughs and misses badly when it reaches 1800 RPM. Mechanic thinks the ProTec ignition is toast. The engine only has 380 hours on it and I am dubious the coil packs could be fried. I also have throttle body injection which I would like to keep. Anyone have anything else to try?? We've now lost most of two boating seasons on this engine and I'd rather not miss any more.

Ditch the ProTec Ignition, the gel packs or whatever they are on that system leak over time and fail.